/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.ql.exec.tez.tools;
import java.io.IOException;
import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.tez.ReduceRecordProcessor;
import org.apache.hadoop.io.BinaryComparable;
import org.apache.tez.runtime.api.Input;
import org.apache.tez.runtime.api.LogicalInput;
import org.apache.tez.runtime.library.api.KeyValuesReader;
/**
* A KeyValuesReader implementation that returns a sorted stream of key-values
* by doing a sorted merge of the key-value in LogicalInputs.
* Tags are in the last byte of the key, so no special handling for tags is required.
* Uses a priority queue to pick the KeyValuesReader of the input that is next in
* sort order.
*/
public class InputMerger implements KeyValuesReader {
public static final Log l4j = LogFactory.getLog(ReduceRecordProcessor.class);
private PriorityQueue<KeyValuesReader> pQueue = null;
private KeyValuesReader nextKVReader = null;
public InputMerger(List<? extends Input> shuffleInputs) throws Exception {
//get KeyValuesReaders from the LogicalInput and add them to priority queue
int initialCapacity = shuffleInputs.size();
pQueue = new PriorityQueue<KeyValuesReader>(initialCapacity, new KVReaderComparator());
for(Input input : shuffleInputs){
addToQueue((KeyValuesReader)input.getReader());
}
}
/**
* Add KeyValuesReader to queue if it has more key-values
* @param kvsReadr
* @throws IOException
*/
private void addToQueue(KeyValuesReader kvsReadr) throws IOException{
if(kvsReadr.next()){
pQueue.add(kvsReadr);
}
}
/**
* @return true if there are more key-values and advances to next key-values
* @throws IOException
*/
public boolean next() throws IOException {
//add the previous nextKVReader back to queue
if(nextKVReader != null){
addToQueue(nextKVReader);
}
//get the new nextKVReader with lowest key
nextKVReader = pQueue.poll();
return nextKVReader != null;
}
public Object getCurrentKey() throws IOException {
return nextKVReader.getCurrentKey();
}
public Iterable<Object> getCurrentValues() throws IOException {
return nextKVReader.getCurrentValues();
}
/**
* Comparator that compares KeyValuesReader on their current key
*/
class KVReaderComparator implements Comparator<KeyValuesReader> {
@Override
public int compare(KeyValuesReader kvReadr1, KeyValuesReader kvReadr2) {
try {
BinaryComparable key1 = (BinaryComparable) kvReadr1.getCurrentKey();
BinaryComparable key2 = (BinaryComparable) kvReadr2.getCurrentKey();
return key1.compareTo(key2);
} catch (IOException e) {
l4j.error("Caught exception while reading shuffle input", e);
//die!
throw new RuntimeException(e);
}
}
}
}